循环剪切作用下三维粗糙裂隙非线性渗流特性数值模拟研究  

Numerical study on nonlinear hydraulic properties of three-dimensional roughjoints under cyclic shear conditions

作　　者：蔚立元[1] 杨瀚清 王晓琳[1] 刘日成[1] 王蓥森 YU Li-yuan;YANG Han-qing;WANG Xiao-lin;LIU Ri-cheng;WANG Ying-sen(State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China)

机构地区：[1]中国矿业大学深地工程智能建造与健康运维全国重点实验室,江苏徐州221116

出　　处：《岩土力学》2023年第9期2757-2766,共10页Rock and Soil Mechanics

基　　金：国家自然科学基金项目(No.51979272,No.52179118);江苏省自然科学基金项目(No.BK20211584);江苏省科技厅科技项目-碳达峰碳中和科技创新专项资金项目(No.BK20220025)。

摘　　要：研究了循环剪切过程中剪切位移和循环次数对三维粗糙裂隙非线性水力特性的影响。首先,基于天然粗糙裂隙面的高程数据生成三维裂隙面,并通过前人的研究结果确定循环剪切过程中的法向位移变化值,建立了16个开度空间模型,从而得到了不同剪切位移和循环次数下接触面积和开度分布情况,发现当循环次数一定时,随着剪切位移的增加,原本吻合的上下表面发生错动,平均开度和各向异性增大,接触面积减小;剪切位移一定时,随着循环次数的增加,上下表面起伏在剪应力作用下被磨平,接触面积增大,平均开度减小。将模型导入数值模拟软件进行计算得到流量数据,结果表明,水力梯度随流量变化规律符合Forchheimer定律。循环1次时,随着剪切位移从4 mm增加到10 mm,线性Fochheimer系数减小了88.3%,非线性Fochheimer系数减小了95.2%;循环2次时,随着剪切位移从4 mm增加到10 mm,线性Fochheimer系数减小了95.4%,非线性Fochheimer系数减小了99.7%,两系数减小的幅度随循环次数增大而增大。进一步分析发现,剪切位移的增加对裂隙渗透性有促进作用,循环次数增加对渗透性起抑制作用。此外,归一化渗透系数随雷诺数变化规律与Zimmerman等提出的预测公式相吻合,且本研究数值模拟计算结果与其公式的拟合系数趋近1,公式中的Fochheimer系数β随剪切位移增大而减小,随循环次数增大而增大。In this study,the effects of shear displacement and the number of cycles on the nonlinear hydraulic characteristics of three-dimensional rough fractures during cyclic shear are studied.First,a three-dimensional fracture surface is generated based on the elevation data of the natural rough fracture surface,and the normal displacement during the process of cyclic shear is determined through previous studies.Sixteen fracture aperture fields are established,so as to obtain the contact area and aperture distribution under different shear displacements and cycles times.It is found that when the number of cycles is fixed,the upper and lower surfaces of the original mesh will stagger with the increase of shear displacement,the average mechanical aperture and anisotropy increase,and the contact area decreases;When the shear displacement is constant,with the increase of the number of cycles,the upper and lower surface undulations are smoothed under the action of shear stress,the contact area increases,and the average mechanical aperture decreases.Finally,the model is imported into the numerical simulation software to calculate the flow rate data.The results show that the hydraulic gradient changes with the flow rate in accordance with Forchheimer's law.With the increase of shear displacement,the linear Fochheimer coefficient decreases by 88.3%,the nonlinear Fochheimer coefficient decreases by 95.2%,the linear Fochheimer coefficient decreases by 95.4%, the nonlinear Fochheimer coefficient decreases by 99.7%, and the reduction rangeof the two coefficients increases with the increase of the number of cycles. Further analysis shows that the increase of sheardisplacement promotes the fracture permeability, while the increase of cycle times inhibits the permeability. In addition, the change ofnormalized transmissivity coefficient with Reynolds number conforms to the research results of Zimmerman et al., and the numericalsimulation calculation results of this study are fitted with the normalized transmissivity coefficient predict

关 键 词：循环剪切 剪切渗流 雷诺数 归一化渗透系数 

分 类 号：TU443[建筑科学—岩土工程]